Check whether double buffering ('bounce buffering') is needed and only do

it if needed.

diff --git a/libsrc/atari/shadow_ram_handlers.s b/libsrc/atari/shadow_ram_handlers.s
index 56ddc76c3fc4d2e50bdac8addf6192ef2d6d851d..adf9085b1a8a82a5cafa7cfe3bf297ffbb31c7e7 100644 (file)
--- a/libsrc/atari/shadow_ram_handlers.s
+++ b/libsrc/atari/shadow_ram_handlers.s
@@ -5,6 +5,7 @@
 ;
 
 DEBUG  =       1
+CHKBUF =       1       ; check if bounce buffering is needed (bounce buffering is always done if set to 0)
 
 .if .defined(__ATARIXL__)
 
@@ -176,6 +177,10 @@ my_RESET_han:
 ; one filename, terminated by "invalid character", located at ICBAL/ICBAH
 
 CIO_filename:
+.if CHKBUF
+       jsr     chk_CIO_buf_fn
+       bcc     CIO_call_a
+.endif
        jsr     setup_zpptr1_y0
        jsr     copy_filename
 CIO_fn_cont:
@@ -193,6 +198,10 @@ CIO_fn_cont:
 ; two filenames, terminated and separated by "invalid character", located at ICBAL/ICBAH
 
 CIO_filename2:
+.if CHKBUF
+       jsr     chk_CIO_buf_fn2
+       bcc     CIO_call_a
+.endif
        jsr     setup_zpptr1_y0
        jsr     copy_filename
        iny
@@ -271,7 +280,10 @@ CIO_read:
        ora     ICBLH,x
        beq     CIO_call_a              ; special I/O through A register in case buffer length is 0
 
-; @@@ TODO: check if bounce buffer is really needed because buffer is in ROM area
+.if CHKBUF
+       jsr     chk_CIO_buf
+       bcc     CIO_call_a
+.endif
 
 ; If the data length is larger than our bounce buffer, we have to split the request into smaller ones.
 ; Otherwise we can get away with one call and a copy to the final destination afterwards.
@@ -431,7 +443,10 @@ CIO_write:
        ora     ICBLH,x
        beq     CIO_call_a_jmp          ; special I/O through A register in case buffer length is 0
 
-; @@@ TODO: check if bounce buffer is really needed because buffer is in ROM area
+.if CHKBUF
+       jsr     chk_CIO_buf
+       bcc     CIO_call_a_jmp
+.endif
 
 ; If the data length is larger than our bounce buffer, we have to split the request into smaller ones.
 ; Otherwise we can get away with a copy to the bounce buffer and the call.
@@ -691,6 +706,125 @@ setup_zpptr1:
        sta     zpptr1+1
        rts
 
+
+.if CHKBUF
+
+; get length of file name pointed to by 'zpptr1'
+; input:   Y - index into file name
+; output:  Y - length
+;          A - destroyed
+get_fn_len:
+       lda     (zpptr1),y
+       beq     @done
+       iny
+       cmp     #ATEOL
+       bne     get_fn_len
+       dey
+@done:
+       rts
+
+
+chk_CIO_buf_fn2:
+       tya
+       pha
+       lda     ICBLL,x
+       pha
+       lda     ICBLH,x
+       pha
+       jsr     setup_zpptr1_y0
+       jsr     get_fn_len
+       iny                     ; include terminating zero
+       bne     fn_cont
+
+chk_CIO_buf_fn:
+       tya
+       pha
+       lda     ICBLL,x
+       pha
+       lda     ICBLH,x
+       pha
+       jsr     setup_zpptr1_y0
+fn_cont:jsr    get_fn_len
+       iny                     ; include terminating zero
+       tya
+       sta     ICBLL,x
+       lda     #0
+       sta     ICBLH,x
+       jsr     chk_CIO_buf
+       pla     
+       sta     ICBLH,x
+       pla     
+       sta     ICBLL,x
+       pla
+       tay
+       rts
+
+
+; check if a CIO input/output buffer overlaps with ROM area (>= $C000)
+; input:                      X - IOCB index
+;      ICBAL/ICBAH/ICBLL/ICBLH - buffer address and length
+; output:                    CF - 1/0 for overlap/no overlap
+;                             A - destroyed
+
+chk_CIO_buf:
+       lda     ICBAH,x
+       cmp     #$c0
+       bcc     @cont
+@ret:  
+.ifdef DEBUG
+       jsr     CIO_buf_noti
+.endif
+       rts
+
+@cont: lda     ICBAL,x
+       clc
+       adc     ICBLL,x
+       lda     ICBAH,x
+       adc     ICBLH,x
+       bcs     @ret            ; ??? wraparound
+       cmp     #$c0
+.ifdef DEBUG
+       jsr     CIO_buf_noti
+.endif
+       rts
+
+.ifdef DEBUG
+; write to screen memory on 2nd line:
+; pos 0: # of accesses without buffering
+; pos 1: # of accesses with buffering
+CIO_buf_noti:
+       php
+       pha
+       tya
+       pha
+       bcc     @nobuf
+
+       inc     CIObnval_dobuf
+       jmp     @cont
+
+@nobuf:        inc     CIObnval_nobuf
+
+@cont: ldy     #40
+       lda     CIObnval_nobuf
+       sta     (SAVMSC),y
+       ldy     #41
+       lda     CIObnval_dobuf
+       sta     (SAVMSC),y
+
+       pla
+       tay
+       pla
+       plp
+       rts
+
+CIObnval_dobuf:
+       .byte   0
+CIObnval_nobuf:
+       .byte   0
+.endif
+
+.endif ; .if CHKBUF
+
 ;---------------------------------------------------------
 
 ; SIO handler
@@ -737,7 +871,10 @@ SIO_call:
 
 SIO_read:
 
-; @@@ TODO: check if bounce buffer is really needed because buffer is in ROM area
+.if CHKBUF
+       jsr     chk_SIO_buf
+       bcc     SIO_call
+.endif
 
 ; we only support transfers <= bounce buffer size
        jsr     cmp_sio_len_bnc_bufsz
@@ -786,7 +923,10 @@ sio_read_ret:
 
 SIO_write:
 
-; @@@ TODO: check if bounce buffer is really needed because buffer is in ROM area
+.if CHKBUF
+       jsr     chk_SIO_buf
+       bcc     SIO_call
+.endif
 
 ; we only support transfers <= bounce buffer size
        jsr     cmp_sio_len_bnc_bufsz
@@ -857,6 +997,72 @@ orgbuf_to_dbuf:
        rts
 
 
+.if CHKBUF
+
+; check if a SIO input/output buffer overlaps with ROM area (>= $C000)
+; input: DBUFLO/DBUFHI/DBYTLO/DBYTHI - buffer address and length
+; output:                         CF - 1/0 for overlap/no overlap
+;                                  A - destroyed
+
+chk_SIO_buf:
+       lda     DBUFHI
+       cmp     #$c0
+       bcc     @cont
+@ret:
+.ifdef DEBUG
+       jsr     SIO_buf_noti
+.endif
+       rts
+
+@cont: lda     DBUFLO
+       clc
+       adc     DBYTLO
+       lda     DBUFHI
+       adc     DBYTHI
+       bcs     @ret            ; ??? wraparound
+       cmp     #$c0
+.ifdef DEBUG
+       jsr     SIO_buf_noti
+.endif
+       rts
+
+.ifdef DEBUG
+; write to screen memory on 2nd line:
+; pos 38: # of accesses without buffering
+; pos 39: # of accesses with buffering
+SIO_buf_noti:
+       php
+       pha
+       tya
+       pha
+       bcc     @nobuf
+
+       inc     SIObnval_dobuf
+       jmp     @cont
+
+@nobuf:        inc     SIObnval_nobuf
+
+@cont: ldy     #78
+       lda     SIObnval_nobuf
+       sta     (SAVMSC),y
+       ldy     #79
+       lda     SIObnval_dobuf
+       sta     (SAVMSC),y
+
+       pla
+       tay
+       pla
+       plp
+       rts
+
+SIObnval_dobuf:
+       .byte   0
+SIObnval_nobuf:
+       .byte   0
+.endif
+
+.endif ; .if CHKBUF
+
 ;---------------------------------------------------------
 
 KEYBDV_handler: